14 



BULLETIN 799^ U. S. DEPAETMEK'T OF AGEICULTURE. 



In rating the averages for the various age classes x was given the 

 valuation of 1, xx of 2, etc. In this manner averages such as 0.32 

 and 2.9 were computed (see Table V) , indicating the average degree 

 of injury. 



Table V. — Relation of injuries to age and to total stand of western ivhite pine 

 on sites of the bottom and slope types.^ 



Age class. 



Bottom sites: 



41 to 60 years.. 

 61 to 80 years. . , 

 81 to lOtf years.. 

 101 to 120 years, 

 121 to 160 years, 

 161 to 200 years 

 201+ years 



Total 



Slope sites: 



41 to 60 years... 

 61 to 80 years.., 

 81 to 100 years.. 

 101 to 120 years 

 121 to 160 years 

 161 to 200 years 

 201+ years 



Total 



Infection traced to — 



Branch 

 stubs. 



Num- 

 ber 







3 



15 

 26 

 137 

 47 

 67 



295 



Per 

 cent.2 







75.0 

 53. 5 

 70.4 

 79.1 

 90.3 

 84.2 



76.7 







75.0 

 62.5 

 63.4 

 78.7 

 57.3 

 97.1 



74.8 



Broken 

 tops. 



Num.- 

 ber. 



Per 

 cent.2 



Frost 

 cracks. 



Num- 

 ber. 



Per 



cent.2 



















1.2 



2.8 



5.3 





 

 

 

 .6 

 3.6 

 



Fire scars 

 and other 

 injuries. 



Num- 

 ber. 



Per 

 cent.2 







25.0 

 46.5 

 29.6 

 19.7 



6.9 

 10.5 



T6tal trees 

 with in- 

 juries to 

 which 

 infection 



was traced . 



Num- 

 ber. 







6.5 

 37.1 

 64.0 



66.7 

 94.7 

 97.4 







25.0 

 37.5 

 36.6 

 20.7 

 39.0 

 2.9 



24.1 







4 



24 



41 



174 



82 



394 



Per 

 cent. 3 



De- 

 gree 

 of 



jury. 



0.32 

 1.74 



Total 

 num- 

 ber 

 of 



trees. 



37 

 62 

 116 



111 



129 



76 



39 







6.66 

 24.4 

 41.0 

 74.0 

 82.8 

 98.6 



55.3 







.16 



.7 

 1.41 

 2.7 

 2.68 

 3.77 



1.9 



50 



100 



235 



99 



70 



712 



1 Percentage of total trees (infected and sound) bearing injuries to total trees in stand = 70. 



2 Percentaee based on total number of infected trees. 



3 Percentage based on total number of trees. 



Table Y shows certain interesting results. On both types of site 

 the infections traced to branch stubs bear the largest percentage 

 over infections traced to other injuries, with 77 per cent for the 

 bottom sites and 75 per cent for the slope sites. Broken tops as 

 sources of original infection were not found, although a considerable 

 number of broken-top trees were recorded and some of these trees 

 gave evidence that a certain amount of infection took place through 

 the exposed tip. In nearly every case it was found that infection 

 in the lower part of the trunk had taken place some time previous 

 to the breakage of the top, as indicated by the difference in the stage 

 of development of the two rotted areas. On the bottom sites ap- 

 proximately 2 per cent of the infections were traced to frost cracks 

 and 22 per cent to miscellaneous injuries, which latter included fire 

 scars, blazes, windfall scars, etc. On the slope sites only 1 per cent 

 of the infections were traced to frost cracks and 24 per cent to 

 miscellaneous injuries. On the slope sites a larger percentage of 

 infection traced to miscellaneous injuries' is found than is recorded 



